import java.util.Scanner;

public class Fibonacci {
    public static void main(String[] args) {
        Scanner sc=new Scanner(System.in);
        int i=sc.nextInt();
        System.out.println(fibonacci(i));
    }

    public static int fibonacci(int num){
        if(num==1||num==2)
        {
            return 1;
        }
        int x=fibonacci(num-1)+fibonacci(num-2);
        return x;
    }
}
